
#include <bits/stdc++.h>

using namespace std;

char S[200], T[200];
int n, ans;

int main() {
  scanf("%d %s %s", &n, S, T);
  for (int i = 0; i < n; ++i)
    if (S[i] != T[i])
      ++ans;
  printf("%d\n", ans);
  return 0;
}
